This invention relates to a colonic overtube for maintaining a section of a colon, such as a sigmoid colon, in a straightened configuration.
The lower gastrointestinal tract comprises the rectum, and the large intestine or colon. The colon, in a textbook arrangement of the human anatomy, extends upwards from the lower right quadrant, traverses the width of the body just below the diaphragm, travels downwards along the left side of the abdomen and then loops in an anterior retrograde manner before linking up with the rectum and the anus.
Even in such a textbook arrangement, the large intestine is difficult to cannulate with a colonoscope due to the flexible nature of the colonoscope and the floppy nature of the colon. This is even more difficult with the more realistic anatomies of actual people.
In some people, the sigmoid colon can be very long and is unfixed, except by its mesentery, and so can be extremely difficult to cannulate due to its predisposition to form loops when a colonoscope is pushed through it. Looping of the colonoscope within the sigmoid colon and transverse colon exacerbates the problems in traversing these areas.
Conventional colonoscopy procedures involve advancing a colonoscope through the floppy sigmoid colon to the proximal end of the descending colon. During advancement of the colonoscope through the sigmoid colon loops often form. It is difficult to then advance the colonoscope further, due to the looped nature of the sigmoid colon. Further pushing of the colonoscope simply increases the loops in the sigmoid colon without advancing the colonoscope into the descending colon.
The sigmoid colon is generally straightened by manipulation of the colonoscope. However advancing the colonoscope further, into the descending colon may cause the loops in the floppy sigmoid colon to reform.
It is known to use an overtube to prevent the reformation of loops by splinting the straightened sigmoid colon. The overtube is typically advanced over the colonoscope until the distal end of the overtube is at the proximal end of the descending colon. The overtube then maintains the sigmoid colon in the straightened configuration and prevents loops from reforming in the sigmoid colon during advancement of the colonoscope further, into the descending colon.
However, due to the potentially tortuous path through a colon, it is often difficult to advance an overtube over a colonoscope without kinking of the overtube occurring.
Furthermore, parts of the interior wall of a colon may become trapped between a colonoscope and an overtube during advancement of the overtube over the colonoscope. This may result in shearing off of the trapped part of the colon wall or puncturing of the colon wall.
In addition, in certain colonoscopy procedures, for example multiple polypectomy, it is necessary to insert and remove a colonoscope several times. This requires considerable skill on the part of the colonoscopist and takes a considerable length of time.
This invention is aimed at providing a colonic overtube which overcomes at least some of these problems.
According to the invention there is provided a colonic overtube for maintaining a section of a colon in a straightened configuration, the overtube having a proximal end for location externally of a colon, a distal end for insertion into a colon, and a colonoscope lumen extending therethrough for passing the overtube over a colonoscope;
at least portion of the overtube being laterally flexible to facilitate flexing of the overtube substantially without kinking during advancement of the overtube through a colon.
The laterally flexible nature of the overtube of the invention enables the overtube to advance through a potentially tortuous path in a colon without kinking. This is particularly advantageous when the overtube is being advanced through a sharp bend in the colon, for example when advancing the overtube through the splenic or hepatic flexures or through parts of the sigmoid colon.
In one embodiment of the invention the laterally flexible portion of the overtube extends along the entire length of the overtube.
In another embodiment of the invention the overtube has more than one laterally flexible portion spaced along the overtube.
The laterally flexible portion may be provided by at least one corrugation. Preferably the corrugation extends along the overtube in a convoluted manner.
The corrugation may extend at least partially circumferentially around the overtube.
In a preferred embodiment of the invention the overtube comprises a plurality of corrugations. Ideally the corrugation is provided on an interior surface of the overtube. Most preferably an exterior surface of the overtube is smooth.
In another embodiment of the invention the overtube comprises a coating of a lubricious material.
The overtube may comprise a composite material. Preferably the overtube is of a layered construction. Ideally the overtube comprises a reinforcement means. The reinforcement means may be embedded in the overtube.
In one case the reinforcement means comprises a coil. In another embodiment the reinforcement means comprises a mesh. The reinforcement means may be of a braided construction.
Desirably the reinforcement means is of a metallic material.
In a preferred embodiment of the invention the overtube is of a material which is thermally stable in use. Ideally the overtube is of polytetrafluoroethylene.
In another preferred case the overtube is extendable between a shortened configuration and an elongated configuration for cannulating at least portion of a colon.
The overtube may comprise a flexible seal at the distal end for sealing between the overtube and a colonoscope extending through the colonoscope lumen.
In another aspect of the invention there is provided a colonic overtube for maintaining a section of a colon in a straightened configuration, the overtube having a proximal end for location externally of a colon, and a distal end for insertion into a colon, and a colonoscope lumen extending therethrough for passing the overtube over a colonoscope;
the overtube comprising a flexible seal at the distal end for sealing between the overtube and a colonoscope extending through the colonoscope lumen.
The colonic overtube of the invention has a flexible seal at the distal end of the overtube. The seal ensures that no parts of the colon wall become trapped between the overtube and the colonoscope during advancement of the overtube over the colonoscope. This arrangement prevents shearing off of the trapped part of the colon wall or puncturing of the colon wall.
In some colonoscopy procedures, air or some other gas is used to insufflate the colon, for example to blow a protruding piece of the wall of the colon laterally to clear a path for advancement of the overtube and/or the colonoscope further distally through the colon. A further advantage of the seal is that it prevents insufflation air from leaking proximally out of the colon between the colonoscope and overtube.
In addition the flexible nature of the seal enables the seal to adapt to the size of the colonoscope to achieve an effective seal between the overtube and the colonoscope for a variety of differently sized colonoscopes.
The seal preferably comprises a film material. The seal may comprise a sheath of film material. Ideally the seal comprises an inner sealing layer and an outer sealing layer around the inner sealing layer. Most preferably the seal is mounted to an exterior surface of the overtube. The seal may extend inwardly to seal between the overtube and a colonoscope extending through the colonoscope lumen. Desirably the seal extends distally of the distal end of the overtube.
According to another aspect of the invention there is provided a colonic overtube for maintaining a section of a colon in a straightened configuration, the overtube having a proximal end for location externally of a colon, a distal end for insertion into a colon, and a colonoscope lumen extending therethrough for passing the overtube over a colonoscope;
the overtube being of a material which is thermally stable in use.
Because the overtube is of a thermally stable material, the stiffness of the overtube may be chosen to be sufficiently flexible for ease of insertion into a colon, and to remain sufficiently stiff within the colon to maintain a section of the colon, such as the sigmoid colon, in a straightened configuration.
The overtube may be of polytetrafluoroethylene.
The overtube is preferably extendable between a shortened configuration and an elongated configuration for cannulating at least portion of a colon.
In a further aspect the invention provides a colonic overtube having a proximal end for location externally of a colon, a distal end for insertion into a colon, and a colonoscope lumen extending therethrough for passing the overtube over a colonoscope;
the overtube being extendable between a shortened configuration and an elongated configuration for cannulating at least portion of a colon.
The overtube according to the invention provides an ergonomic and easily workable means of cannulating the colon as far distally as the caecum, without requiring a long, awkward length of tubing externally of the colon.
In one embodiment of the invention in the shortened configuration at least portion of the overtube is retracted in a concertina-like manner.
In another embodiment of the invention the overtube comprises a plurality of overtube sections which are movable relative to one another to extend the overtube to the elongated configuration. The overtube sections may be releasably mountable to one another to extend the overtube to the elongated configuration.
In another case the overtube comprises an actuator to extend the overtube in situ to the elongated configuration. Preferably the actuator may be activated from externally of a colon. Ideally the actuator comprises a connector for extending from the overtube within a colon to a location externally of the colon. Most preferably the connector extends from the distal end of the overtube. The connector may be anchored to the overtube. Preferably the connector comprises a drawstring. Ideally the drawstring is configured to be looped through a working channel of a colonoscope to a location externally of a colonoscope.
In a further embodiment of the invention the overtube comprises a rounded tip at the distal end for atraumatic advancement of the overtube through a colon. The tip may be mounted to the overtube. Preferably the tip is mounted to an exterior surface of the overtube. Ideally the tip extends around the distal end of the overtube at least partially into the colonoscope lumen.
The rounded tip at the distal end of the overtube ensures that the overtube advances atraumatically through the colon. Any inadvertent contact between the distal end of the overtube and the interior wall of the colon will not result in damage or trauma to the colon.
In a preferred case the overtube comprises at least one exchange lumen for exchange of fluid and/or a medical device through the lumen. The overtube may comprise means to view a colon distally of the overtube, the viewing means being at least partially provided in the exchange lumen. The overtube may comprise means to insufflate a colon, the exchange lumen providing an insufflation channel. Preferably the overtube comprises means to flush a colon, the exchange lumen providing a flushing channel. Ideally the overtube comprises means to illuminate a colon, the illumination means being at least partially provided in the exchange lumen.
In a further embodiment of the invention the overtube comprises limiting means to prevent complete insertion of the overtube into a colon. The position of the limiting means on the overtube may be adjustable. Preferably the limiting means is releasably mounted to the overtube. Ideally the limiting means is threadably mounted to the overtube. Most preferably the limiting means comprises a flange.
In a preferred embodiment of the invention the overtube has a discontinuous interior surface for ease of passage of the overtube over a colonoscope. Ideally the overtube comprises one or more inwardly projecting elements on the interior surface for contacting a colonoscope. The projecting element may comprise a corrugation. In another case the projecting element comprises a protruding strip.
The projecting element may extend longitudinally along the overtube. The projecting element may extend at least partially circumferentially around the overtube. The projecting element may extend along the overtube in a convoluted manner.
In one embodiment the projecting element comprises a plurality of discrete protrusions.
In a preferred embodiment of the invention the colonic overtube may be used for maintaining a sigmoid colon in a straightened configuration.
In a further aspect of the invention there is provided a method of performing a colonoscopy procedure, the method comprising the steps of:
inserting a colonoscope into a colon and advancing the colonoscope through at least part of the colon;
straightening a section of the colon;
advancing a colonic overtube over the colonoscope to maintain the section of the colon in a straightened configuration;
advancing the colonoscope to a point distally of the straightened section of colon; and
advancing the overtube over the colonoscope to a point distally of the straightened section of colon.
In one embodiment of the invention the method comprises the step of withdrawing the colonoscope from the colon while the overtube remains in place in the colon. The method may comprise the step of advancing a medical device through the overtube to access a point in the colon distally of the straightened section of colon.
Preferably the method comprises the step of mounting the overtube to the colonoscope before inserting the colonoscope into the colon.
In one case the overtube is advanced by extending the overtube from a shortened configuration to an elongated configuration. The overtube may be advanced by pushing the overtube from externally of the colon.
In a preferred case the section of colon being straightened is the sigmoid colon.
Ideally the overtube is advanced to a point distally of the descending colon.
The overtube provides a bridge between the fixed rectum and the fixed descending colon over the floppy sigmoid colon, thus preventing loops from reforming in the sigmoid colon. Furthermore, the overtube provides a bridge between the fixed descending colon and the fixed ascending colon over the floppy transverse colon, thus preventing loops from reforming in the transverse colon. Using the overtube of the invention advancement of a colonoscope through a colon as far as the caecum is easier and quicker, and causes less discomfort to a patient.
For an overtube to successfully splint a straightened sigmoid colon, its stiffness must be above the minimum threshold of stiffness required to prevent sigmoid loops from re-forming as the colonoscope is passed through the colonoscope lumen, and advanced further into the colon.
However it is also desirable that the overtube is not overly stiff, as insertion of the overtube becomes more difficult due to friction as the stiffness increases. This is because a xe2x80x9cstraightenedxe2x80x9d sigmoid colon is never perfectly straight. Consequently it is almost impossible to introduce a completely rigid overtube over the colonoscope. Some degree of compliance is required by the overtube.
While an overtube measured at room temperature may appear stiff enough to successfully splint a straightened sigmoid colon, this may no longer be the case at body temperature. Known overtube materials show a dramatic drop in stiffness between ambient room temperature and body temperature. In order for an overtube made from such materials to splint the sigmoid colon, it will have to be made overly rigid, so that it is still above the minimum threshold of stiffness required to prevent sigmoid loops from re-forming at body temperature. This excess rigidity causes serious insertion difficulties due to friction. Alternatively, if an overtube made from such materials was made less stiff, it may be easier to insert, but may not be stiff enough at body temperature to successfully splint the straightened sigmoid colon.
The overtube of the invention is configured to be relatively thermally stable. In this way the overtube at room temperature (insertion temperature) is selected to be sufficiently compliant or floppy to be easily inserted into a colon over a colonoscope. There is then a minimal drop in stiffness between ambient room temperature and body temperature compared to other materials, so that at body temperature the overtube is above the minimum threshold of stiffness required to prevent sigmoid loops from reforming.
Two other features of the overtube aid the insertion process: (a) corrugations, which minimise frictional contact with the scope; (b) extremely low friction PTFE material used in its construction.